Environmental apparatus



Dec. 21, 1965 R. s. CHAMBERLIN ETAL 3,224,277

ENVIRONMENTAL APPARATUS Filed Feb. 16, 1962 2 Sheets- Sheet I De 1965 I R. s. CHAMBERLIN ETAL 3,224,277

ENVIRONMENTAL APPARATUS I Filed Feb. 16, 1962 2 Sheets- Sheet 2 United States Patent 3,224,277 ENVIRONMENTAL APPARATUS Robert S. Chamberlin, La Grange, Ill., and Lyle V. Larsen, Summit, N.J., assignors to Chicago Bridge '8: Iron Company, Chicago, 111., a corporation of Illinois FiledFeb. 16, 1962, Ser. No. 173,652 8 Claims. (Cl. 73-432) "The present invention relates generally to environmental apparatus and more particularlyto special leak tight chambers used in simulating environments such as those existing in outer space.

Outer space simulation requires a test environment having an extremely low pressure in the order of 1x10- mm. of mercury or lower and a wall temperature ap proaching that of liquid nitrogen -320 F.

Because one cubic inch of air at atmospheric pressure will expand to 760,000,000 cubic inches (440,000 cubic feet or a volume over 9 feet square at the base and towering one mile high) at 1x10 mm. of'mercury and 60 F., the vessel within which this environment is being simulated has required an extremely high degree of leak tightness and the system must include sophisticated and expensive vacuum pumping equipment.

The inside of the vessel and those items within'it must also be constructed of materials that are free of or can easily be made free of moisture from the air or other materials which will vaporize at the low pressure in the vessel. Such moisture is undesirable because it limits the degree of vacuum that can be attained with a reasonable pumping system. Moisture is held on the surface of the vessel until extremely low vacuums are reached, thereby requiring handling, by the pumps, of greatly expanded vapor volumes (e.g., one drop of water would expand to almost 220,000,000 cubic feet of vapor at 1X10 mm. of mercury and 60 F.).

Ordinary space simulation chambers for producing the low vacuum indicated above, and sufiiciently large for a person to enter for maintenance or hook-up purposes, are normally constructed of stainless steel, the inner surface of which is highly polished and thoroughly cleaned. A sectionalized separate wall containing liquid nitrogencarrying channels is installed inside the chamber, spaced from the outer or main chamber Wall, and provides the desired temperature environment.

The inner surface of the sectionalized low temperature wall, facing a test object within the chamber, is provided with a black, heat absorbent surface. The inside walls outer surface, facing the main chamber wall, is polished to reduce to a minimum the amount of heat accepted from the relatively Warm chamber wall. This reduces the amount of liquid nitrogen consumed in lowering the temperature because it reduces heat transfer by radiation from the outer chamber wall. Liquid nitrogen is not introduced into the sectionalized low temperature walls until a degree of vacuum is reached at which heat transfer by convection and conduction is insignificant.

The vacuum pumping equipment for these ordinary chambers is atttched through piping to the main chamber wall. Generous openings are provided between individual sections of the low temperature wall to permit free flow of the air molecules, during the later stages of pumping, from a test area within the low temperature wall to pumping ports in the outer chamber wall.

Provision is usually made to circulate heated gas through the channels in the low temperature wall to drive off atmospheric moisture picked up on the absorbent black surface. The cleaned and-polished inner surface of the main chamber wall is necessary to reduce moisture pick-up to within tolerable limits. Periodic cleaning of all surfaces and rigid cleanliness procedures are required to keep other contaminants to a minimum. Elaborate and costly leak testing methods must be used to establish the required tightness of the main chamber, of all of its fittings, of the low temperature wall panels, and of associated piping; and all must be near perfect.

The present invention provides a space simulating system constituting spaced inner and outer chambers, 1ncluding means for providing and maintaining temperature and pressure within the inner chamber at the low levels desired. The advantages of the subject system over ordinary chambers are many. In a space simulation system constructed in accordance with the present invention, the main chamber and low temperature walls can be of less critical materials, finishes and cleanliness; less pumping capacity will be required to attain the desired vacuum; the leak tightness of all elements between the inner and outer walls will be less critical; and the liquid nitrogen usage will be reduced. Lower installation and operating costs together with better performance are thereby obtained.

Other features and advantages of the subject apparatus will become apparent to those skilled in the art from the following detailed description in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a perspective view, partially cut away, showing a space simulation system constructed in accordance with the present invention;

FIGURE 2 is a vertical sectional view of the system'of FIGURE 1;

FIGURE 3 is an enlarged fragmentary sectional view illustrating one embodiment of a wall portion of the subject system;

FIGURE 4 is a fragmentary sectional view illustrating another embodiment of a wall portion of the subject system; and

FIGURE 5 is a fragmentary vertical sectional view, similar to FIGURE 2, illustrating another embodiment of a space simulation system constructed in accordance with the present invention.

Referring initially to FIGURES 1 and 2, there is illustrated an embodiment 10 of a space simulation system or apparatus constructed in accordance with the present invention and comprising a spherical outer chamber 11 spaced from and surrounding an interior chamber 12 within which is located a plurality of posts 13 for supporting an article 14 such as a space vehicle to be subjected, within chamber 12, to temperature and pressure conditions typical of those existing in outer space.

The interior of inner chamber 12 is evacuated to a low pressure (eg about 1 10"" mm. Hg or lower) by diffusion pumps 16 located below apparatus 10, in communication with the interior of inner chamber 12, and connected by conduit 22 to conventional mechanical roughing pumps illustrated diagrammatically in FIG- URE 2. The space 15 between outer chamber 11 and inner chamber 12 is evacuated to a pressure between that in inner chamber 12 and that outside chamber 11, to provide a guard vacuum, by a roughing pump communicating with space 15 through a connection 17. If desired, connection 17 and conduit 22 may be connected to the same roughing pump (e.g., see FIGURE 2) a typical embodiment of which is illustrated in Orr U.S. application Serial No. 104,478, filed April 20, 1961, now Patent No.3,154,138.

Space 15 between the inner and outer chambers is evacuated to a pressure somewhat higher than that Within inner chamber 12, but still relatively low. Provision of a guard vacuum within the space 15 substantially lessens the leakage of air into the interior of inner chamber 12 from the atmosphere. More specifically, the likelihood of leakage is diminished by the ratio of pressures on opposite sides of a chamber. Accordingly, assuming a pressure within space 15 of 1X10 mm. Hg, the likelihood of leakage from the atmosphere into space 15 is of the ratio 760/l 1() Assuming a pressure within inner chamber 12 of 1x10 mm. Hg, the likelihood of leakage from space 15 into the interior of inner chamber 12 is of the ratio l 1O- /l l0- By providing a guard vacuum in space 15, the likelihood of leakage is much less than if no guard vacuum were provided, in which case the likelihood of leakage would be of the ratio 760/ 1 10 Thus, by providing a space simula tion system with spaced exterior and interior chambers, and by providing a guard vacuum in the space between the chambers so that the difference in pressure on opposite sides of the wall of either chamber is reduced to a minimum, the likelihood of leakage of gas from the atmosphere into the interior of the inner chamber is re duced substantially.

Refer-ring to FIGURES 2 and 3, inner chamber 12 is provided with a pair of walls 18, 19 having mutually opposed surfaces, each spaced from the other along substantially their entire areas to define a continuous channel 20 therebetween through which a temperature regulating fluid, such as liquid or gaseous nitrogen, may be circulated. Channel 20 extends substantially continuously in all directions along the periphery of inner chamber 12.

To prevent outgassing from the walls of chamber 12 into the interior thereof when the interior pressure is very low, a temperature regulating fluid such as gaseous nitrogen is circulated through channel 20 to bake out the walls defining the channel. Baking out walls 18, 19 causes gases entrapped in the walls to be expelled into the interior of chamber 12 where the gases are removed by pumps 16, or into space 15, between the outer and inner chambers, where the gas is removed by the roughing pump communicating with connection 17. Thus when the pressure within the interior of inner chamber 12 is reduced to the extremely low level of outer space, the likelihood of outgassing by the walls 18, 19 into the interior of chamber 12 is minimal, because the gases in these walls have been previously baked out and removed from apparatus 10.

The roughing pump communication with connection 17 Will reduce the pressure in space 15 to a level at which the gaseous molecules are so few, that heat transfer by convection is insignificant. At such pressure levels (e.g. l 10 mm. Hg) radiation is the only vehicle for heat transfer from the atmosphere to interior chamber 12. Means are provided, in accordance with the present invention, to reduce heat transfer by radiation to a minimum, said means being illustrated in FIGURES 3 and 4.

FIGURE 3 illustrates radiation-preventing means 30 in the form of a plurality of layers of thin aluminum sheets located adjacent the interior surface of outer chamber 11. A substantial portion of the heat radiated inwardly from the inner surface of outer chamber 11 is reflected back outwardly by the aluminum layer closest thereto. Only a fraction of theheat radiated inwardly from the inner surface of chamber 11 is radiated further inwardly by the first layer of aluminum. Whatever heat is radiated inwardly by the first layer of aluminum encounters the second layer of aluminum, which reflects back a portion of the radiation from the first layer. Progressing inwardly through the layers of aluminum, less and less heat is radiated inwardly until at the innermost layer of aluminum the amount being radiated inwardly is insignificant.

FIGURE 4 illustrates another embodiment of radiation-preventing insulation means 31 in the form of a porous material such as pearlite filling the space between the inner and outer chambers. Material 31 cuts down the amount of radiation reaching inner chamber 12 to insignificant amounts.

The provision of radiation-impeding material 30 or 31 eliminates the necessity of constructing the outer chamber of a shiny material such as stainless steel. In accordance with the present invention, outer chamber 11 may be constructed of the more economical carbon steel. The interior chamber 12 should be constructed of a material which is relatively ductile at extremely low temperatures, e.g. stainless steel, copper, aluminum, aluminum alloy, or the like.

In the embodiment 10 illustrated in FIGURES 1 and 2, diffusion pumps 16 are located outside of the outer chamber 11, and communicate with the interior of inner chamber 12 through a sleeve 32 extending through an opening in the bottom of the inner chamber. Located within sleeve 32 is a baflle or trap 33, cooled by liquid nitrogen, for preventing oil fumes from diffusion pumps 16 from entering the interior of chamber 12. Posts 13 are located at the top of sleeve 32.

In another embodiment 40 illustrated in FIGURE 5, the diffusion pumps 46 are mounted on the sides of a substantially cylindrical inner chamber 42, communicate with the interior of the inner chamber, and discharge into the space 45 between inner chamber 42 and an outer chamber 41. In this embodiment space 45 serves as a manifold for all of the diffusion pumps 46, and the manifold 45 is in turn evacuated by a mechanical roughing pump (not shown).

Describing apparatus 10 now in greater detail, reference is made to FIGURES 1 and 2 wherein the apparatus is shown to be supported in a recessed foundation 50 by posts 51; and to be provided with support ti es 56 extending between the exterior of inner chamber 12 and the interior of outer chamber 11.

Located between the edge of the opening in the bottom of interior chamber 12 and sleeve 32 is a flexible annular expansion joint 58 constituting a seal between the sleeve and the opening. Located within inner chamber 12 are gas-molecule-freezing shields 54 maintained at extremely low temperatures by vaned tubing through which a liquid cryogen such as helium is circulated. Gaseous molecules remaining within chamber 11 after it has been evacuated will, in their random movement, probably eventually strike the shields 54 which are cold enough to cause the molecules to freeze thereto.

In the embodiment 10 of FIGURES 1 and 2, outer chamber 11 is divided into upper and lower spherical sections terminating at flanges 65, 66 respectively. Inner chamber 12 is also divided into upper and lower spherical sections terminating at flanges 67, 68 respectively. When the apparatus is in operation, the two sections of each chamber are joined together along the flanges. When it is desired to introduce into or remove from chamber 12 an article 14, apparatus 10 is dismantled by dividing each of the chambers along a line defined by the adjacent flanges 65, 66 and 67, 68.

There have thus been described typical embodiments of a space simulation system or apparatus for reproducing low temperature and pressure conditions such as those existing in outer space. It should be noted that apparatus of this type need not be limited to use as a space-simulating system, but may be used for any purpose in which low temperature and pressure conditions are required. The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

What is claimed is: 1. Environmental apparatus comprising: an outer chamber constructed of carbon steel; an inner chamber located entirely within said outer chamber and constructed of a metallic material relatively ductile at the temperature of liquid nitrogen;

said inner chamber having inner and outer walls with mutually opposed surfaces spaced apart along the entire areas of said surfaces to define channel means therebetween;

said chambers including means defining a space therebetween;

means for evacuating the space between said chambers to a pressure level where heat transfer by convection is not significant;

means for evacuating the interior of the inner chamber to a pressure level substantially lower than that in the space between the two chambers;

and insulating means between the chambers for impeding heat transfer by radiation inwardly toward the inner chamber.

2. Apparatus as recited in claim 1 wherein said insulating means comprises a multiplicity of layers of thin aluminum sheet located adjacent the interior surface of the outer chamber.

3. Apparatus as recited in claim 1 wherein said insulating means comprises a porous material filling the space between said chambers.

4. Apparatus as recited in claim 1 wherein said means for evacuating the interior of the inner chamber comprises diffusion pumps located entirely within and discharging into the space between the two chambers.

5. Apparatus as recited in claim 1 wherein:

said means for evacuating the space between the chambers comprises a roughing pump and means for connecting said space with a roughing pump;

said means for evacuating the interior of the inner chamber comprises a diffusion pump in communication with the interior of the inner chamber, and means for connecting said diffusion pump to the same roughing pump to which the space between the chambers is connected.

6. Apparatus as recited in claim 1 wherein said inner chamber is constructed of metallic material selected from the group consisting essentially of stainless steel, copper, aluminum, and aluminum alloys.

7. Apparatus as recited in claim 1 and comprising:

an opening in the bottom of said inner chamber;

a sleeve extending upwardly through said opening into said inner chamber;

a flexible annular expanison joint constituting a seal between the exterior of said sleeve and the edge of said opening;

means at the top of said sleeve for supporting an article within said chamber;

said means for evacuating the inner chamber being in communication with said sleeve;

and fume-baflling means in said sleeve between said inner chamber and the evacuating means for the inner chamber.

8. Apparatus as recited in claim 1 wherein:

said channel means encompasses substantially the entire peripheral area of said inner chamber;

and said channel means extends substantially continuously in all directions along the periphery of the inner chamber.

References Cited by the Examiner UNITED STATES PATENTS 3,007,596 11/1961 Matsch 2209 3,010,220 11/1961 Schueller 73432 3,018,561 l/1962 Wells 73432 3,078,708 2/1963 McClintock 73-15.6

RICHARD C. QUEISSER, Primary Examiner.

DAVID SCHONBERG, Examiner. 

1. ENVIRONMENTAL APPARATUS COMPRISING: AN OUTER CHAMBER CONSTRUCTED OF CARBON STEEL; AN INNER CHAMBER LOCATED ENTIRELY WITHIN SAID OUTER CHAMBER AND CONSTRUCTED OF A METALLIC MATERIAL RELATIVELY DUCTILE AT THE TEMPERATURE OF LIQUID NITROGEN; SAID INNER CHAMBER HAVING INNER AND OUTER WALLS WITH MUTUALLY OPPOSED SURFACES SPACED APART ALONG THE ENTIRE MEANS OF SAID SURFACES TO DEFINE CHANNEL MEANS THEREBETWEEN; SAID CHAMBERS INCLUDING MEANS DEFINING A SPACE THEREBETWEEN; MEANS FOR EVACUATING THE SPACE BETWEEN SAID CHAMBERS TO A PRESSURE LEVEL WHERE HEAT TRANSFER BY CONVECTION IS NOT SIGNIFICANT; MEANS FOR EVACUATING THE INTERIOR OF THE INNER CHAMBER TO A PRESSURE LEVEL SUBSTANTIALLY LOWER THAN THAT IN THE SPACE BETWEEN THE TWO CHAMBERS; AN INSULATING MEANS BETWEEN THE CHAMBERS FOR IMPEDING HEAT TRANSFER BY RADIATION INWARDLY TOWARD THE INNER CHAMBER. 